Internal combustion engines such as those for motorcycles typically have an oil pump that is a dry sump-type system with two sets of intermeshing external rotary gears. The gears are typically driven on a common drive shaft with one gear set supplying pressurized oil to the engine for lubrication, with the other gear set scavenging excess oil from the crankcase to the oil tank. Oftentimes, the oil pump does not provide sufficient oil for the engine, especially through certain RPM ranges. In other applications, performance modifications may be made to the engine that require increased oil flow to provide proper lubrication as the stock oil pump does not have sufficient capacity.
In order to accommodate increased oil flow, a simple solution is to provide a larger capacity oil pump. However, a larger capacity pump requires additional space that may not be available and prevents retrofitting to an existing engine. Therefore, it is desirable to utilize an oil pump having the same space requirements as a stock pump. It is also desirable to mount to the existing drive shaft to minimize the modifications required to mount to the engine. If an existing oil pump is used, one modification that provides increased flow is to widen the gear sets or increase the depth of the gears. However, clearance constraints may prohibit widening of the gears or may limit the depth of the gears. Another solution is to increase the angular velocity of the gears. This method of providing increased flow is undesirable as it may increase the wear of the current pump and require more maintenance. It also requires increasing the angular velocity of the drive shaft or adding a gear intermediate the drive shaft and the pump gears.
Another alternative is to change the gear profile. A typical stock oil pump gear includes fourteen teeth, as shown in FIG. 1. An improved gear tooth profile may provide for pumping a larger volume of oil and maintaining a higher oil pressure, overcoming the pressure problems associated with some engines. An improved gear tooth profile could provide for utilizing gears that may replace the stock gears and provide improved flow with an identical outer radius and RPM.
Another problem with existing oil pumps is that the ratio between oil supply volume and oil return volume is not optimized. Under some operating conditions, the engine may be overwhelmed by oil. The crankcase then becomes filled, resulting in oil carryover, wherein excessive oil is blown out of the crankcase breather.
It can be seen that a new pump is needed that provides improved flow over existing designs. Such an oil pump should provide increased oil flow without requiring additional space for the oil pump. Such a design should provide for retrofitting existing oil pumps with an improved gear tooth profile, resulting in increased oil pumping volume. Such a system should provide for optimization of the pump flow for the supply as well as the pump flow ratio between the supply and the return. The present invention addresses these as well as other problems related to oil pumps for internal combustion engines.